Background Restenosis is one of the most important factor to worsen patients��� prognosis after PCI. There have been several big advancements in preventing restenosis such as DES. But, diagnosis of restenosis largely depends on the invasive coronary angiography. We���ve tried to elucidate the clinical usefulness of the MIBI/Tl-201 dual isotope SPECT image to detect restenosis and temporal change of the perfusion state before and after PCI. Method and Result 1) We reviewed 135 coroanry artery territories of 45patients who underwent SPECT before 6mo follow-up angiography. 20 of them performed SPECT before PCI and temporal chage were investigated in these patients. Restenosis was difined as more than 50% stenosis at the target lesion. We investigated the sensitivity and specifity of SPECT for detection of restenosis and they were 62% and 63% respectively. Sensitivity and specificity related to the vascular territories were : LAD territory (53%,36%), LCx territory(50%,82%), RCA territory(67%, 79%). Mean diameter stenosis of the lesions of positive SPECT results was not significantly different PCI-performed lesions and in de novo lesion. (73짹5.4%, 63.5짹12.4%, p>0.1) 2) We investigated the temporal change of the perfusion state of SPECT image in 60 coronary territories of 20 patients. Interestingly was no significant interval change in perfusion score both in restenotic lesion territory and in patent lesion territory. Conclusion: 1) MIBI/Tl201 dual isotope SPECT was only moderately sensitive and specific for detection restenosis. 2) Myocardial perfusion state measured by perfusion score was not significantly changed after PCI both in restenotic lesion and in patent lesion.